Synthetic salmon calcitonin was evaluated in 23 patients with hypercalcemia of different causes treated continuously or intermittently for periods from one day to two months. Clinically important decreases in serum calcium level were achieved in 17. The response was only partial; often the serum calcium descended from dangerously high levels to a tolerable range or to minimal hypercalcemia. The drug was nontoxic, and hypersensitivity did not occur, in spite of recommencement of therapy after days or weeks of cessation. Salmon calcitonin was found to be particularly useful as an initial emergency drug for hypercalcemic patients with heart failure or azotemia or both. It often facilitated the clinical improvement that was necessary for these patients to tolerate more definitive therapy or other hypocalcemic agents.